Method for separating liquid mixtures



May 3, 1966 D. L. CHILDS METHOD FOR SEPARATING LIQUID MIXTURES OriginalFiled July 27, 1959 2 Sheets-Sheet 1 INVENTOR.

DAVID L. CHILDS 1 O'M A TTORNE Y3 y 1966 D. CHILDS 3,249,295

METHOD FOR SEPARATING LIQUID MIXTURES Original Filed July 27, 1959 2Sheets-Sheet 2 INVENTOR. DAVID L. CHILDS l M 0 m2 ATTORNEYS UnitedStates Patent METHOD FOR SEPARATING LIQUID MIXTURES David ,L. Childs,Birmingham, Micln, assignor of onethird to Giovanni Raccuglia, Prospect,Ky., and onethird to James J. Shanley, Bethesda, Md.

Original application July 27, 1959, Ser. No. 829,599, now Patent No.3,133,881, dated May 19, 1964. Divided and this application Mar. 10,1964, Ser. No. 354,815

6 Claims. (Cl. 233-20) This patent application is a division ofapplicants co-' pending parent patent application Serial No. 829,599,tiled July 27, 1959, now Patent No. 3,133,881.

The present invention relates to the centrifugal separation of liquids.More particularly, the present invention relates to a new method forseparating liquids by centrifugation and storing separated components.Further the present invention involves a new method for collecting ofnutrient media, tissue fractionation, and the research fractionation ofmilk and the separation of virus and bacteria therefrom. Perhaps thechief utility of the invention is in collection and separation of wholeblood and storage of blood components, and the invention will beillustrated by way of example in this connection.

As is well known, whole blood is a fiuid tissue comprised of a varietyof solid particles suspended in colloidal plasma. Chief among thesuspended particles are the red cells, the white cells, and theplatelets. Suspension of the solid particles is maintained by vascularcirculation in a parent organism. Whole blood is not a true dispersion,as evidenced by the spontaneous sedimentation of quiescent blood.

Accordingly, it is not difficult to effect a gross separation of severalof the formed elements of blood from each other and from the plasma bycentrifugation, which is nothing more than accelerated sedimentation.Such separation has great utility in a number of biologicalapplications, such as plasmapheresis, relief of thrombocyto- -in storedblood. The various components of stored Whole blood have differentsurvival times, and the useful life of stored blood for certain purposesis largely limited to these survival times. For example, the plateletshave an ordinary survival time of only a few days.

More recently, it has been found that platelet survival can be greatlyextended, with good viability, if the platelets are separately stored,as in a simple gelatin solution and at reduced temperature. Not only isthe survival time of certain blood components extended by separatestorage, but also the remaining components of ordinarily long survivalmay be separately stored for long periods without special treatmentother than refrigeration.

Another difficulty arising from the use of whole blood stored withanticoagulant is encountered in those therapies in which an excessivevolume of anticoagulant is amazes Patented May 3, 1966 "Icecontraindicated. [In such cases, partial experimental evidence indicatesthat the prompt separation of the blood components may remove or greatlyreduce, where possible in respect to other conditions, the need foranticoagulant. The platelets may be roughly considered to be coagulatingagents, inasmuch as upon lysis they liberate accelerators for thetransformation of prothrombin to thrombin and for the conversion offibrinogen to fibrin by thrombin. Hence, the separation of bloodcomponents followed by reconstitution minus platelets should result inthe production of a blood which has less tendency to coagulate in theabsence of anticoagulants.

These and other applications render the fractionation of blood of greatimportance.

In the past, separation has been achieved largely by one of threemethods. 'In the earliest method, blood obtained by phlebotomy wascollected in a closed and evacuated donor bottle and then transferredfrom the'bottle to a centrifuge. This method had the advantage that theonly equipment needed at the time of phlebotomy was a simple donorbottle and donor kit. The centrifuge could be centrally located andcould handle the contents of a number of bottles during the timeconsumed by a single phlebotomy. Separation was followed by bulk storageand/or packaging of the separated fractions for therapeutic use. Simpleas this method was, it suffered from the great disadvantages thatasepsis could be maintained only with the greatest difficulty and thatthe frothing induced during handling increased the danger of embolism.

In recent years, a system for blood separation has been developed inwhich fresh blood passes directly from the donor through a closed systemincluding a centrifuge. This new system has largely overcome the problemof turbulence and provides closed-system sterility, but it hasnecessitated the use of costly equipment which can be employed inconjunction with only a single phlebotomy at a time. Unless donors aremeticulously scheduled so that a plurality of the same blood type areprocessed sequentially, then this equipment must be cleaned after eachphlebotomy to prevent the mixing of blood types.

Still more recently, the fractionation of blood has been carried out ona commercial scale using plastic bags in which the red cell fraction andthe plasma fraction are separated either by sedimentation or bycentrifuging. The plasma fraction is then expelled from the bag bysqueezing. However, this plastic bag technique as presently practicedhas many inconveniences, principally that the segregation of the twofractions after separation is a slow and burdensome procedure.

The present invention provides a method which is simple and thereforeinexpensive while at the same time 7 it has the advantages of the closedsystem asepsis and freedom from excessive handling of the blood. Theseresults are achieved by providing a methodin which a receptor bottle hasa plurality of compartments with provision for transferring a separatedcomponent from one compartment to another during centrifuging, thefractionation and segregation of components being accomplished by thedesign and position of the parts and their manipulation duringcentrifuging.

It is an important objectof the present invention to provide a methodfor the centrifugal separation of liquids which will permit separationof the liquids into two or three components in a closed system duringcentrifuging.

Another important object of the present invention is the provision of amethod for the centrifugal separation of liquids in which flexible bagcomponents are centrifuged around an axis of rotation passing through atleast one bag component.

Another important object of the present invention is the provision of amethod for the centrifugal separation of liquids in which the volumetriccapacity of a component of the systemdetermines the extent ofsegregation.

Other objects and advantages of the present invention will becomeapparent from a consideration of the following description, taken inconjunction with the accompany ing drawings, in which:

FIGURE 1 is a view generally in section taken along the line 1'1 ofFIGURE 2 with some parts in elevation of a system capable of carryingout the present invention;

FIGURE 2 is a view in cross section taken on the line 22 of FIGURE 1;

FIGURE 3 is an enlarged detail view of the valve and valve actuatorshown in FIGURES 1 and 2;

FIGURE 4 is an enlarged detail view of the mechanical latch and magneticrelease shown in FIGURE 1;

FIGURE 5 is a view in section taken on the line 5-5 of FIGURE 4;

FIGURE 6 is an enlarged detail view of a modified form of valve;

FIGURE 7 is a view in section taken along the line 77 of FIGURE 8showing a modification of the system illustrated in FIGURES 1-4,inclusive, capable of carrying out a variant of the method of theinvention; and

FIGURE 8 is a view in cross section taken on the line 8-43 of FIGURE 7.

Referring now to the drawings in greater detail, and specifically to thevariant of FIGURES 1-5, inclusive, there is shown a system adapted tocarry out the method of the present invention. Centrifuge element 10 isin the form of an open top chuck carried on centrifuge drive shaft 12,the latter being-connected to a source of power for rotating thecentrifuge element 10 about the axis -0, which axis coincides with themajor axis of centrifuge element 10. Removably carried within centrifugeelement or chuck 10 is a centrifuge cup 14 which fits snugly withinchuck 10 so as to be readily withdrawable but is prevented from rotatingrelative to chuck 10' by provision of keying element 16 integral withcup 14- and slideably received in keyway 18 of chuck 10. Cup 14 has aninternal annular ledge 20 which supports a dividing wall orpartition'indicated generally at 22 which is made up of two separableportions 24 and 26. Cup 14 comprises a cover 28 carrying a resilientsealing washer or gasket 30 and an annular depending flange 32, thelower end of which rests on and maintains partition 22 in place onshoulder 20. A plurality of fastening means 34 are movable into and outof cover fastening position, these fastening members being retained incover fastening position against centrifugal forces by compression ofresilient gasket 30. p

In the lower portion of cup 14, there is a follower indicated generallyat 36 having a flat bottle supporting plate 38 and an annular dependingflange 40 which is snugly received in sliding relation by the internalwall surfaces of the lower portion of cup '14. Within the hollowinterior of follower 36 as thus formed and urging the follower upwardlyis a spring 44. Depending from the lower surface of plate 38 is arestraining member 46 made up of a hollow cylinder having a latchengaging upwardly facing annular shoulder 48 at the lower end.

Referring more particularly to FIGURE 4, a latch device is indicatedgenerally at 50 having duplicate latch members 52 pivoted at their lowerends in lugs 54 carried by the bottom of cup 14, latch members -2including catch or detent elements 56 engageable in latchingrelationship with annular shoulder 48 of restraining member 46'. Alinking spring 58 pulls the upper ends of latch members 52 toward oneanother. A magnetic armature 60 has grooves. 61 receiving latch members52, the bottoms of grooves 61 presenting cam surfaces 62 engaging camsurfaces 63 on latch elements 52. Armature 60 is upwardly urged byspring 64 to cause cam surfaces 62 to press latch members 52 outwardlyagainst the action of spring 58 into latching position. Spring 64 isdenecessary that the side walls be collapsible.

signed so as not to urge armature 60- higher than the position shown inFIGURE 4 whether or not restraining member 46is in latching position. Itwill be apparent that downward movement of armature 6tl'will permitspring 58 to pull latch members 52 out of latching engagement withshoulders 48 of restraining member 46 and upward movement of magneticarmature 60 will urge these members into latching position whenrestraining member 46 is in its lowermost position. The coacting anglesof the cam surfaces61 and 63 are such that downward movement ofrestraining member 46 Will move the latching members 52 against theaction of spring 64 until they are in latching position in engagementwithshoulder 48.

Ribs 66 may be formed projecting out of the inside wall surface of theupper portion of main compartment 27 in cup 14, these ribs being sodimensioned that their lower ends form a stop to control desired orextreme upward movementof follower 36.

Main chamber 27 of cup 14 is designed to. receive a flexible bloodbottle or bag of any desirable shape when empty so long as it can bereceived within compartment 27 when filled. The usual 500 cc. capacityblood bag would be suitable. This blood bag may be entirely flexible ormay have one or two rigid end walls. It is Chamber 33 is designed toreceive a smaller bag element than bag element 68 and such a bag element70 with flexible or rigid end walls is shown. As is usual practice withsome types of blood bags, the two bag elements are joined by a severableflexible tubing 72, the portion 74 of this tubing adjacent bag element68 opening into the main compartment 69 formed by the interior of bagelement 68, on axis 0-0. In the present embodiment, tubing portion 74incorporates a spring-pressed ball valve indicated generally at 76,normally urged into closed position. The means for closing this tubingportion 74 can take several forms while still fulfilling its function inthe present combination. Partition 22 has on its upper surface aconvoluted groove 78 which snugly receives the coils of tubing 72.'Tubing 72 can open into second compartment 71, formed by the interior ofbag element 70, at the lower portion of the peripheral extremity or inany other location convenient for storing the coiled tubing with outkinking.

Although cup 14 is peripherally sealed by gasket 30,

provision is made for fluid 'intercommunication between main chamber 27and second chamber 33. Thus, a

small slot 80 in partition 22 in the region of shoulder 20 and a similarslot 82 in the lower edge of depending annular flange 32 assure freeflow of fluid between main chamber 27 and secondary chamber 33 at pointsfarthest removed from the axis 0-0 .of rotation. A bleeder port 83 onaxis O--O in cover 23 may be used to place the entire interior of cup 14in communication with the atmosphere.

Since the present invention calls for operations of valve 76 and/ orlatch means 50 at a desired time during centrifugation, remotecontrol-means for these purposes are provided. Magnetic armature 60which operates latching means 50 is moved downwardly at the desiredmoment during centrifuging by energization of the electromagnet 84. Thismagnet with its electrical winding 85 is im bedded in a hardened plasticmaterial 86 in a recess 88 in the bottom wall of centrifuge chuck 10.One end of the electrical winding is grounded on the centrifuge chuckwhich, together with the shaft 12, is electrically conductive andgrounded. The other lead 90, insulated from the centrifuge structure,goes to a collector ring 92 rigidly mounted on and insulated from shaft12. A collector brush 94 and lead 96 go to a timer switch control box 98and thence through a lead 100 to one terminal of a battery 102 havingits other terminal grounded. At least the portion of centrifuge cup 14between electromagnet 84 and magnetic armature 64) is formed ofnonmagnetic material. Thus when timer switch 98 operates to complete theelectrical circuit, electromagnet 84 pulls armature 60 into itslowermost position thereby unlatching latch member 46 and permittingspring 44 to urge follower member 36 upwardly against the bottom of bag68.

Valve 76 is made up of a magnetic ball 104 urged by spring 106 againstvalve seat 108. Provision is made for operating this valve at anydesired time by means of an electromagnet 110 imbedded in the plastic112 in a recess 114 of member 26 of partition 22. It is to be noted froman inspection of the drawings that portion 74 of tubing 72 whichincorporates valve76 is snugly received by opening 77 in partition 22 soas to position the valve accurately relative to the electromagnet and toposition the opening of tube portion 74 into bag 68 on axis OO. One endof the electrical winding 116 on the magnet is grounded on partition 22,which together with centrifuge cup 14 is electrically conductive andgrounded through chuck 10. The other end of the electrical winding 116is carried through an insulated cable 118 out of cup 14 to a jack 120'on chuck through a jack plug 122 to present a readily disconnectableelectrical connection between the electrical circuit of the centrifugecup and the electrical circuit of the centrifuge chuck. An insulatedcable 124 carries the circuit down through chuck 10 to a collector ring126 rigidly but insulatingly mounted on shaft 12. A brush 128 carriesthe circuit to a timer switch control box 130 and from there to groundthrough conduit 100 and battery 102. The timer switches 98 and 130 canbe of any conventional type which can be independently set to hold acricuit open or closed for set periods of time or to close and open acircuit at set time intervals.

In use, the bottle made up of bag sections 68 and '70 is used for aphlebotomy in the same manner as the conventional plastic bags andexcept Where valve 76 is present, bag sections 68 and 70 can be theconventional plastic bags of the type described in Gardner, Howell &Hersch in the J. Lab. & Clin. Med. 43:196-207, 1954 and by Klein,Arnold, Earl & Wake in New England Journal of Medicine, 254:1132-1133,1956.

The blood collects in the main compartment 69 formed by the interior ofbag 68 and cannot flow into the second compartment 71 formed by theinterior of bag 70 because of valve 76. Main compartment 69 usuallyincludes a liquid anti-coagulant and this and the blood usually bringthe quantity of liquid in bag section 68 to around 500 cc. in volume.The bag entry means for the blood (not shown) is sealed off in anydesirable manner depending upon its type and the bag is ready to beplaced in centrifuge cup 14. At this time, cover 28 and partition 22 areremoved from the cup to accommodate bag section 68 in' cup chamber 27.Where latch means 50 is not present, bag section 68 is forced downagainst follower 36 and the action of spring 44 until partition 22 canbe inserted and rest on shoulders 20. In the insertion of partition 22,tubing portion 74 is carefully placed in the opening shown between thehalves of the partition. The tubing 72 is arranged in the convolutedgroove 78 and bag section 70 is arranged in cup chamber 33- in such away that it can expand, it being empty and deflated at this time. Thedepending annular flange 32 on cover 28 holds the partition in itsproper position and fasteners 34 can be turned into locking positionwhen gasket 30 is compressed. Jack plug 122 is inserted in jack 120 andthe equipment is ready for the centrifuging process.

The centrifuging speed and time is such as to separate the red cellfraction and the plasma fraction, the latter preferably containing theplatelets in effective quantity. After a given period of time,determined by experience, a separation of the red cell fraction and theplasma fraction has been effected and at this point timer 130 closes theelectrical circuit to energize magnet 110. The magnetic flux path causesball 104 to move away from valve seat 108 against the action of spring106. Spring 44 acting on follower 38 thereupon causes a progressivecollapsing of bag section 68 to reduce the volume of the compartment 69by ejecting the plasma fraction through tubing 72 into secondcompartment 71. Air bleeder port 83 permits bag section 70 to increasein size and collect the plasma fraction but of course fluid from chamber33 must move into chamber 27 to fill the space left by collapsing bagelement 68. A filler member 132 of variable thickness can be used in theupper portion of cup chamber 3-3 to determine the final volume of secondcompartment 71. This filler member 132 can be varied in thickness inaccordance with the amount of whole blood originally in bag section 68and the percentage of red ceils in the blood being centrifuged. In thismanner, when the desired volume of plasma has been transferred to thesecond compartment 71, the action of spring 44 will no longer have anyeffect because the hydrostatic pressure, exclusive of earthsgravitational force, in the two bags will be balanced. In such case, rib66 need not be long enough to interfere with upward action of follower36. When transfer of the platelet fraction has taken place, the requiredtime being determined by experience, timer 130 cut off electrical energyto magnet and spring 106 closes valve 104.

If only red cell pack and plasma fraction segregation are desired, thebag can be removed from the centrifuge at this time and placed instorage either with the sections connected together or with the tubingsealed in two places and severed in between. If platelet recovery isdesired, centrifugati'on is continued at a suitable speed for separatinga platelet pack on the side walls of second compartment 71. In this typeoperation, timer can be set so that valve 104 stays open after theplasma is transferred and while the platelets are being separated. Whena platelet pack has been collected, the centrifuge is stopped and thebag sections are removed. As soon as tubing section 74 moves away fromthe vicinity of magnet 110, valve 104 closes. As the bag elements aretaken out of cup 14, plasma is transferred by gravity back into the maincompartment to form a reconstituted blood by moving partition section 26to bring energized magnet 110 into proximity to valve 76 to open thevalve. If the plasma fraction is to be separately stored, valve 104remains closed during platelet separation and the plasma is withdrawnfrom second compartment 71 in any suitable manner.

Instead of the volume of centrifuge cup chamber 33 determining theamount of plasma transferred, the lower end of rib 66 can be utilized toaccomplish this purpose so long as chamber 33 is large enough to takeall the plasma fraction. I

Where latch members 46 and 50 are used, the procedure can be the same asabove except that bag section 68 need not be forced into cup chamber 27.In this operation timer 98 is set to operate after the centrifuge cup isloaded and closed and preferably not later than the point in time atwhich timer 130 operates to open valve 104. The operation of timerswitches 98 and 130 can be synchronous.

As pointed out later, it may in some cases be advisable to use a liquidsuch as Water in centrifuge cup 14 in this method of operation in orderto take up the difference in volume between the available space in cupchambers 27 and 33 and the volume of liquid in the main compartment 69.In the case of water, the specific gravity of the plastic material andthe blood fractions being greater than that of water, the bag sectionswill be moved by centrifugal force to their extreme outer positionsrelative to axis OO. Port 83 may be omitted.

Where restraining member 46 and latching member 50 are used, valve 76can be omitted entirely. In such case, timer switch 130 and magnet 110are present but not used. It will be obvious that at the proper momentduring centrifuging when the plasma fraction is to be transferred timerswitch 98 operates to energize magnet 84 and this releases follower 36.Thereupon spring 44 proceeds to transfer the plasma until the volume ofthe second compartment in bag element 70 is filled or until follower 36comes up against the lower end of rib 66, whichever by design happensfirst.

In the operation described in the last paragraph, the absence of a valvein tubing section 74 adjacent the main compartment in bag section 68 maycause some inconvenience in handling and operating the 'device. It maybe desirable in such instance to use a non-magnetic spring-pressed valveas shown in FIGURE 6 which is urged into closing position againstpressure in the main compartment of bag section 68 with a forcesufficient to prevent blood from passing into tubing 72 during handlingof the two bag sections but with this spring force being such thataction of follower spring 44 will force plasma fraction through thevalve. The valve parts in FIGURE 6 corresponding to those in FIGURE 3have been given the same reference'nu-merals plus one.

The structure of the system illustrated in FIGURES 7 and 8 is the sameas that illustrated in FIGURES 1-5, inclusive, except in the region ofthe partition in the centrifuge cup and the point at which liquid isejected from the main compartment. To simplify the drawing and thedescription only those portions of the system of FIGURES 7 and 8 areillustrated which differ in structure and function'from the system ofFIGURES 1-5, inclusive. To further simplify the description, the samereference numerals are used in FIGURES 7 and 8 as those in FIGURES l-5,inclusive, but where the structure is different 100 is added to eachnumeral or the numeral is primed.

It will be apparent that instead of the outlet from bag section 168being on axis -0 in- FIGURES 7 and 8,

this outlet and therefore section 174 of tubing 172 is at the outermostperiphery of the upper part of bag section 168. This makes it possibleto form partition 22 in one piece with a slot 177 for receiving tubingsection 176. A filler block (not shown) may be used in slot 177 to holdtubing section 176 against radial movement due to centrifugal forcesduring centrifuging. The opening in bag section 170 in which tubing 172terminates is at the periphery'of the bottom portion of this bagalthough it could be otherwise located.

Operations with the variant of FIGURES 7 and 8 are the same as those ofFIGURES 1-5, inclusive, except as now pointed out. Since tubing 174opens into the periphcry of bag section 168 at a point farthest removedfrom axis OO, centrifugal force will eject red cell fraction out of themain compartment 169 when valve 176 is opened after separation has takenplace and segregation is desired. If follower 36 is latched down at thistime, red cell fraction will continue to be ejected until thehydrostatic pressure in the second compartment 171 at the entry openingequals that at the corresponding opening to tubing section 174. pressureentering through bleeder port 83 will cause bag section 168 to collapse.The volume of chamber 33 can be designed so that this balance ofpressures takes place when all the .red cells and a safety layer ofplasma fraction have been transferred into second compartment 171.

Preferably, follower 36 is used so that a more positive bag control willbe present and so that the volume of compartment 171 will determine theextent of transfer rather than the balancing of weights of liquidagainst one another. Of course, in this type operation the lower ends ofrib 66 are above the highest point reached by follower 36 during thetransferring action and therefore In the meantime, atmospheric serveonly to.limit extreme movement of follower 36 the plasma fraction incompartment 169 when transfer has been completed.

It may be desirable in some cases in respect to both variants to add asmall amount of water to the interior of centrifuge cup 14 to preventisolated portions of the bag walls from being subjected to highlyconcentrated stresses and to keep the tubing from being kinked orpinched. Tubing with no liquid in it may be collapsed by hydrostaticpressure in the water during centrifuging but the centrifugalhydrostatic pressure in the blood com-. ponent entering the tubing willreinfiate it due to resilience of the tubing and the greater specificgravity of the blood components relative to the water. Of course, wherespring 44 is also acting on main bag sections 68 or 168, the additionalhydrostatic pressure within the blood component entering the tubing willalso act to reinflate the tubing. Also important, this slight amount ofwater around the peripheryof main compartment 27 will facilitate peelingof the bag wall away from the centrifuge cup wall as the follower 36moves upwardly.

In both described variants, chamber 27 is large enough with follower36in its lowermost position to hold a full blood bag and in this respectwhere follower 36 is unlatched after the centrifuge cup 14 is loaded andcover 28 locked in place, the resilience of spring 44 produces achamber. above the follower 36 which precisely accommodates bag section68 or 168: during centrifuging. The redv cell pack in normal human bloodoccupies about 45% of the volume normally occupied by whole blood. Whenthe usual volume of anticoagulant is taken into account, the red cellfraction plus a safety layer of plasma occupy about 45% of the volume ofthe entire liquid. It follows that stops 66 permit follower '36 tocollapse bag section 68 to reduce the volume of main compartment 69 tothis amount when stops 66 are used for this purpose in the embodiment ofFIGURES 1-6, inclusive. Where the volume of chamber 33 is used to limitthe transfer of a blood component in either modification, ribs 66 can beomitted. This is especially the case in the embodiment of FIGURES 7 and8 where centrifugal force ejects the red cell fraction and a safetylayer of plasma so long as there is space available in secondcompartment 171, as

dictated by the volume of chamber 33 or the balance of hydrostaticpressures.

The environment and the practice described in copending applicationSerial No. 802,398, filed March 27, 1959, now Patent 3,190,546, issuedJune 22, 1965 to Giovanni Raccuglia, David L. Childs and James I.Shanley correspond to that of the present case. Thus in respect to thevariant illustrated in FIGURES 1-6, inclusive, plasma is transferred tothe second compartment 71 until only red cell fraction and a safety coreof plasma remain in main compartment 68. I This means that not more than55% of the volume of the whole blood originally in main com- .partment69 is transferred into second compartment 71.

A smaller percentage down to as low as 25% of the total initial wholeblood volume may be all that is transferred into the second compartmentbut in general the maximum amount of plasma, consistent with freedomfrom red cells, is transferred. It is only because of the variations inthe amount of blood initially present in main compartment 69 and thevariations in red cell content from one donor to another that areasonable safety fraction of plasma must remain with the red cellfraction. As pointed out above, thevolurne of chamber '33 may be variedto accommodate these two factors by inclusion of a filler disk 132 ofthe proper thickness, a plurality of these disks of graduatedthicknesses being available for this purpose.

The terminology'concentric to an axis as used in this specification andclaims in referring to the side walls of a container or bottle isintended to embrace any wall structure which coincides with a continuoussurface generated by points rotating in circles in an infinite number ofplanes normal to the axis, with the centers of the circles lying alongthe axis of revolution, each such plane passing through the continuoussurface only once.

The terms revolve and revolution are used herein to embrace both theturning of a body around an axis outside the body and the turning of abody about an axis passing through the body while the terms rotate androtation are used to designate only turning of a body around an axispassing through the body. Where the term density is used in respect tothe liquids being handled, apparent density is included within themeaning of the term since, as has been pointed out earlier, blood comprises solid particles suspended in colloidal plasma.

The presence of some gas in the bag sections initially will notadversely influence the methods of the present invention.

Although the present invention has been described in connection withpreferred variants, it is to be understood that variations may beresorted to without departing from the spirit of the invent-ion, asthose skilled in this art will readily understand. Such variations areto be considered within the purview and scope of the invention asdefined by the appended claims. I

What is claimed is: Y

1. The method of separating liquid mixtures into fractions of greaterdensity and lesser density comprising the steps of:

(a) providing a centrifuge having a container holding member revolvablearound an axis of revolution,

(b) providing a container separate from the centrifuge having a firstcompartment containing a discrete body of liquid mixture and a secondcompartment, the compartments being interconnected by continuouspassageway means,

() placing the container in the container holding member of thecentrifuge, with both compartments held by the member for synchronousrevolution around the axis of revolution, and with the discrete body ofliquid mixture confined entirely to the first compartment,

(d) revolving the container holding member and both of the compartmentssynchronously around the axis of revolution for a period of time untilthe discrete body of liquid mixture While confined entirely to the firstcompartment forms within the first compartment a first fractional liquidbody of more dense fraction resting against a wall of the firstcompartment remote from the axis of revolution and a second fractionalliquid body of less dense fraction supported by the first fractionalliquid body and between the first fractional liquid body and the axis ofrevolution,

(e) then while continuing to revolve the container holding member andboth compartments around the axis of revolution utilizing hydrostaticpressure within one fractional liquid body to transfer liquid fractionfrom the one fractional liquid body out of the first compartment throughthe continuous passageway means into the synchronously revolving secondcompartment,

(f) continuing to revolve the container holding memher and bothcompartments around the axis of revolution and continuing transfer ofliquid fraction through the continuous passageway means untilhydrostatic pressure in the liquid in the second compartment adjacentthe passageway means including the effect of the liquid in thepassageway means exactly balances hydrostatic pressure in the liquid inthe first compartment adjacent the passageway means, and

(g) collecting and holding all the transferred liquid fraction withinthe second compartment for a period during centrifuging. 2. The methodas set out in claim 1 in which the liquid fraction transferred is lessdense fraction.

3. The method as set out in claim 1 in which the liquid fractiontransferred is more dense fraction.

4. The method of separating liquid mixtures into fractions of greaterdensity and lesser density comprising the steps of (a) providing acentrifuge having a container holding member revolvable around an axisof revolution, (b) providing a container separate from the centrifugehaving a first compartment containing a discrete body of liquid mixtureand a second compartment, the compartments being interconnected bycontinuous passageway means,

(c) placing the container in the container holding member of thecentrifuge, with both compartments held by the member for synchronousrevolution around the axis of revolution, and with the discrete body ofliquid mixture confined entirely to the first compartment,

(d) revolving the container holding member and both I of thecompartments synchronously around the axis of revolution for a period oftime until the discrete body of liquid mixture While confined entirelyto the first com-partment forms within the first compartment a firstfractional liquid body of more dense fraction resting against a wall ofthe first compartment remote from the axis of revolution and a secondfractional liquid body of less dense fraction supported by the firstfractional liquid body and between the first fractional liquid body andthe axis of revolution,

(c) then while continuing to revolve the container holding member andboth compartments around the axis of revolution exerting force on a wallportion of the first compartment to reduce the volumetric liquidcapacity of the first compartment to thereby transfer liquid fractionfrom the one fractional liquid body out of the first compartment throughthe continuous passageway means into the synchronously revolving secondcompartment, and (f) collecting and holding all'the transferred liquidfraction within the second compartment for a period during centrifuging.5. The method of claim 4 in which the liquid fraction transferred isless dense fraction.

6. The method of claim 4 in which the liquid fraction transferred ismore dense fraction.

References Cited by the Examiner UNITED STATES PATENTS 1,132,814 3/1915Weston et al. 233-20 1,296,399 3/1919 Johansson 233-27 1,534,604 4/1925Ter Meer 233-47 1,695,990 12/ 1928 Altpeter 233-47 2,533,806 12/1950Holzapfel. 2,636,646 4/ 1953 Olsen 220-205 X 2,661,150 12/1953 Abbott.

2,678,159 5/1954 Ellis 233-27 X 2,702,034 2/ 1955 Walter.

2,822,126 2/1958 Cohn 233-46 X 2,848,995 8/1958 Ryan 128-214 2,906,4519/ 1959 Tullis et a1. .233-27 3,064,647 11/ 1962 Earl.

3,096,283 7/1963 Hein 233-20 M. CARY NELSON, Primary Examiner.

ROBERT F. BURNETT, Examiner.

1. THE METHOD OF SEPARATING LIQUID MIXTURES INTO FRACTIONS OF GREATERDENSITY AND LESSER DENSITY COMPRISING THE STEPS OF: (A) PROVIDING ACENTRIFUGE HAVING A CONTAINER HOLDING MEMBER REVOLVABLE AROUND AN AXISOF REVOLUTION, (B) A PROVIDING A CONTAINER SEPARATE FROM THE CENTRIFUGEHAVING A FIRST COMPARTMENT CONTAINING A DISCRETE BODY OF LIQUID MIXTUREAND A SECOND COMPARTMENT, THE COMPARTMENTS BEING INTERCONNECTED BYCONTINUOUS PASSAGEWAY MEANS, (C) PLACING THE CONTAINER IN THE CONTAINERHOLDING MEMBER OF THE CENTRIFUGE, WITH BOTH COMPARTMENTS HELD BY THEMEMER FOR SYNCHRONOUS REVOLUTION AROUND THE AXIS OF REVOLUTION, AND WITHTHE DISCRETE BODY OF LIQUID MIXTURE CONFINED ENTIRELY TO THE FIRSTCOMPARTMENT, (D) REVOLVING THE CONTAINER HOLDING MEMBER AND BOTH OF THECOMPARTMENTS SYNCHRONOUSLY AROUND THE AXIS OF REVOLUTION FOR A PERIOD OFTIME UNTIL TH DISCRETE BODY OF LIQUID MIXTURE WHILE CONFINED ENTIRELY TOTHE FIRST COMPARTMENT FORMS WITHIN THE FIRST COMPARTMENT A FIRSTFRACTIONAL LIQUID BODY OF MORE DENSE FRACTION RESTING AGAINST A WALL OFTHE FIRST COMPARTMENT REMOTE FROM THE AXIS OF REVOLUTION AND A SECONDFRICTIONAL LIQUID BODY OF LESS DENSE FACTION SUPPORTED BY THE FIRSTFRACTIONAL LIQUID BODY AND BETWEEN THE FIRST FRACTIONAL LIQUID BODY ANDTHE AXIS OF REVOLUTION, (E) THEN WHILE CONTINUING TO REVOLVE THECONTAINER HOLDING MEMBER AND BOTH COMPARTMENTS AROUND THE AXIS OFREVOLUTION UTILIZING HYDROSTATIC PRESSURE WITH IN ONE FRACTIONAL LIQUIDBODY TO TRANSFER LIQUID FRACTION FROM THE ONE FRACTIONAL LIQUID BODY OUTTO THE FIRST COMPARTMENT THROUGH THE CONTINUOUS PASSAGEWAY MEANS INTOTHE SYNCHRONOUSLY REVOLVING SECOND COMPARTMENT, (F) CONTINUING TOREVOLVE THE CONTAINER HOLDING MEMBER AND BOTH COMPARTMENT AROUND THEAXIS OF REVOLUTION AND CONTINUING TRANSFER OF LIQUID FRACTION THROUGHTHE CONTINUOUS PASSAGEWAY MEANS UNTIL HYDROSTATIC PRESSURE IN THE LIQUIDIN THE SECOND COMPARTMENT ADJACENT THE PASSAGEWAY MEANS INCLUDING THEEFECT OF THE LIQUID IN THE PASSAGEWAY MEANS EXACTLY BALANCES HYDROSTATICPRESSURE IN THE LIQUID IN THE FIRST COMPARTMENT ADJACENT THE PASSAGEWAYMEANS, AND (G) COLLECTING AND HOLDING ALL THE TRANFERRED LIQUID FRACTIONWITHIN THE SECOND COMPARTMENT FOR A PERIOD DURING CENTRIFUGING.